Analysis Of Pipe-Soil Interaction Of SCR And Fatigue Of TDP

As the development of global industry, the demand for oil and gas is increasing. Onshore oil and gas and offshore oil and gas have been far from satisfying the needs, development of deep sea oil and gas has become the focus of the world.The oil and gas resource is extremely rich in South China Sea,development of marine resources becomes the focus of research.Touchdown point (TDP) is the site of SCR initially contacting with the seabed, linking Sag Bend and Flow Line. Although the tension of TDP is minimun of whole Sag Bend, but under the influence of the marine enviroment and the movement of the top, as TDP interacting with seabed soil, TDP is the hot spot of SCR fatigue analysis.In this thesis, the domestic and foreign experiments research and numerical simulation progress of steel catenary riser are first summarized, the research progress of SCR fatigue analysis is also introduced.Second, the article summarized the fatigue analysis methods for marine structures and pipe-soil interaction analysis methods, with emphasis on the simulation of seabed soil feature curve and fatigue analysis method based on crack growth calcution.Then, the pipe-soil static interaction is simulated with finite difference method, the influence factors of top displacement, soil suction ,soil stiffness are studyed. The results are compared to Hodder's experiment results.Next, with the non-linear spring elements in software ANSYS, the pipe-soil interaction under repeated loading is researched, also the phenomena of trench depth increasing is simulated .In this research, simplified soil hysteresis model is used.It can be found that increasing of trench depth will influence the mechanical properties such as bending moment, vonMises stress along the pipe.At last, the dynamic characteristics of steel catenary riser under top cyclic vertical load are calculated with the finite element method. Unique curve model of crack growth rate is applied to calculate the crack propagation curve of the surface crack in TDP, factors that affect the fatigue crack growth life are analyzed.